The cellular slime mold, Dictyostelium discoideum, is unique in that the ameboid cells live independently during the initial growth phase of development. Subsequently in response to a chemotactic substance cyclic AMP, aggregation of the amoeboid cells results in the formation of multicellular pseudoplasmodia. At this stage as a result of cell contacts, the amoebae differentiate into prestalk and prespore cells and within a few hours a mature sorocarp composed of mature stalk and pore cells is produced. The proposed research involves a study of glycoprotein synthesis during development of D. discoideum and certain aggregateless mutants. Sugars such as 3H-L-fucose will be used to label the glycoproteins. A major problem which will be investigated concerns the stage of the cell cycle at which glycoprotein is synthesized as the synthesis of glycoprotein appears to be related to the processes of cell division during the vegetative stage and to cell differentiaton at a later stage. In addition a study will be conducted to determine the effect of a specific antiserum (Fab), which blocks certain cell-cell contact sites, on the differentiation of prespore cells in D. discoideum.